It depends on the particular gun as well as what you are striving for.
To just buy a beater and figure to 'refinish' it, resell and make some money,,most times you won't if you paid someone else to do the work.
If you do the work yourself and do a great job, yes there can be a profit in there. You often have to dismiss your hourly rate when done as it won't reflect what the kids at Micky's are getting in many cases.
Refinish work can be a great hobby. It can be a full time job.
The latter should lean towards restoration quality work however if you want to draw customers willing to pay what you are worth in labor.
Many in the fulltime line end up specializing in a few areas in house and the rest gets sent out to others that specialize in those needs.
But if like to do the work and see it as fun & fulfilling use of time, then go to it.
Not everyone looks at hand polishing a complete S&W H/E to bring it back to it's old sharp edged, flat surfaced, sharp lettered self as something to look forward to.
But we're out there.
...and not every gun needs to be brought back to a 100%'r either.
Many only need proper mechanical repairs and touch ups to finish, holes filled, stuff like that.
But that's real restoration work and not many do that now.
It's easier to be a parts changer, refinish everything and call it a full restoration.